(a) Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display having a bent alignment of liquid crystal molecules to obtain a wide viewing angle and a fast response time.
(b) Description of the Related Art
Liquid crystal displays typically include a first substrate having common electrodes and a color filter, and a second substrate having thin film transistors and pixel electrodes. The first substrate and the second substrate are provided substantially in parallel with a predetermined gap therebetween, and liquid crystal is injected between the two opposing substrates. An electric field is formed between the substrates by applying different voltages to the pixel electrodes and common electrodes. Accordingly, the alignment of liquid crystal molecules of the liquid crystal material is varied to thereby control the transmittance of incident light.
Various types of liquid crystal displays have been developed to improve response times and viewing angle. They include the HAN (hybrid aligned nematic) mode liquid crystal display and the OCB (optically compensated bend) mode liquid crystal display. The OCB mode LCD includes an electrode formed on each opposing substrate, the electrodes acting to form an electric field that is perpendicular to the two substrates; liquid crystal injected between the two substrates; and an alignment layer formed on each substrate, the alignment layers providing a force to align the liquid crystal molecules in a direction substantially parallel to the two substrates.
In the OCB mode LCD, a symmetrical arrangement is realized about an imaginary center plane between the two substrates and parallel to the same. That is, the liquid crystal molecules are aligned substantially parallel to the substrates, then are increasingly slanted until reaching this center plane where the liquid crystal molecules are substantially perpendicular to the two substrates. A wide viewing angle is achieved as a result. To obtain such a bent alignment of the liquid crystal molecules, a horizontal alignment agent that is oriented in the same direction is used and a high voltage is initially applied. Also, since the liquid crystal molecules move in the same orientation when the LCD is operated, a wide viewing angle and a fast response time are realized.
However, in such a LCD, in areas where unit pixels begin, a smooth bending alignment of the liquid crystal molecules cannot be aligned in a smooth bending pattern, thereby limiting the display characteristics. This is a result of the opposing directions of the bending alignment of the liquid crystal molecules and the bending direction of the electric field at edges of the pixel electrodes. That is, unlike the common electrode, which is formed over an entire surface of the substrate, the pixel electrodes are divided for each pixel region such that this opposing direction of LC molecule alignment and electric field occurs at the edges of the pixel electrodes.